Lift your wheel off the ground and give it a spin. If the wheel wobbles back and forth or up and down, it’s time to true it. Wheels come out of true through regular use. The rim is held at the correct angle to the hub by the pull of the spokes in equal directions. Hopping curbs, hitting rocks and the general punishment a bicycle endures is enough to knock a wheel out of true.

A freewheel makes it possible to coast on a bike. When you are pedaling, the freewheel engages the sprockets, but it allows the rear wheel to turn when the pedals are at rest.

- A bicycle stand is always recommended
- A special tool designed specifically for your particular freewheel, known as a “freewheel puller”
- An adjustable wrench compatible with the hexagonal section of your freewheel puller
- You may need a bench-mounted vice for particularly stubborn freewheels

The Schrader valve is the type you will find on an automobile. Schrader valves are still used in some bicycle applications, but have become less popular because their size requires the drilling of a larger hole which significantly weakens narrow rims. The spring mechanism that keeps air inside a Schrader valve is also problematic for riders using compact pumps. A Presta valve can be identified by its smaller diameter and the locknut that is permanently attached to the tip of the valve.

A freehub is attached to the rear hub of your bicycle. It is a spinning mechanism designed to hold the cassette. Coasting when the pedals are at rest and pedaling are possible thanks to the freehub.

Start by removing the cassette. To remove the cassette:

The rear derailleur is designed to move the chain up and down on the sprockets (or cogs) connected to your rear hub. Together these cogs are known as the rear cassette. By moving to a cog with fewer teeth, the derailleur gives the rider a faster (or higher) gear which is appropriate for flat areas or descents. By moving to a cog with more teeth, the derailleur offers a gear more appropriate for climbing hills (or a lower gear).

A chain “stretches” through regular use. This does not mean the metal literally stretches, but over time the bushings between the plates of the chain wear down, and the chain becomes a little longer. “Stretch” is the main reason avid cyclists replace their chains, but if your chain is rusty or just plain ol’ grimy, it’s not a bad idea to replace it.